Paper discharge tray for aligning sheets

ABSTRACT

A paper discharge tray includes a placing part on which a recording medium discharged from a paper discharge part is placed; and a projection which is provided on the placing part and includes plural apexes arranged in a paper discharge direction of the recording medium.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority from Provisional U.S. Application 61/540,499 filed on Sep. 28, 2011 the entire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a paper discharge tray for aligning and receiving sheets discharged after image formation is performed.

BACKGROUND

An image forming apparatus, such as a copying machine or a printer, includes a paper discharge tray for receiving sheets after image formation is performed. A certain paper discharge tray includes a projection on a tray surface in order to align sheets in order of discharge and to place them on the tray surface by reducing the stiffness of the discharged sheets.

Plural types of sheets different in material or size are processed by the image forming apparatus, and the stiffness varies according to the sheet type or temperature/humidity environment and the like. If the stiffness of the sheets is high, even if the projection is provided on the tray surface, the sheets are not aligned, and there is a fear that the sequence of pages is changed, or the sheets become disordered on the tray surface.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic structural view showing an MFP including a paper discharge tray of an embodiment;

FIG. 2 is a schematic side view showing corrugation roller pairs of the embodiment;

FIG. 3 is a schematic explanatory view showing sheet alignment by a projection of the paper discharge tray of the embodiment;

FIG. 4 is a schematic explanatory view showing sheet alignment by a rib of a paper discharge tray of a comparative example; and

FIG. 5 is a schematic explanatory view showing a rib of a modified example.

DETAILED DESCRIPTION

In general, according to one embodiment, a paper discharge tray includes a placing part on which a recording medium discharged from a paper discharge part is placed; and a projection which is provided on the placing part and includes plural apexes arranged in a paper discharge direction of the recording medium.

Hereinafter, an embodiment will be described. FIG. 1 is a schematic structural view showing an MFP (Multi Function Peripheral) 10 as an example of an image forming apparatus including a paper discharge tray 30 of an embodiment. The MFP 10 includes a printer part 11 as an image forming part, a scanner part 12 and a paper feeding part 13.

The paper feeding part 13 includes first and second paper feed cassettes 13 a and 13 b. The paper feed cassettes 13 a and 13 b can feed both an unused sheet and a reused sheet (sheet whose image is decolored by a decolorable process).

The printer part 11 includes a charging device 16 to uniformly charge a photoconductive drum 14 rotating in an arrow m direction, and a laser exposure device 17 to form an electrostatic latent image on the photoconductive drum 14 by irradiating a laser beam 17 a based on image data or the like from the scanner part 12 to the charged photoconductive drum 14. The printer part 11 includes a developing device 18 to supply toner to the electrostatic latent image on the photoconductive drum 14, a transfer device 20 to transfer a toner image formed on the photoconductive drum 14 to a sheet P as a recording medium, and a cleaner 21. The printer part 11 includes a fuser 22 between the photoconductive drum 14 and the paper discharge tray 30.

The scanner part 12 includes a document cover 12 b, optically reads a document on a document table 12 a, converts an optical signal into an electric signal, and sends the signal to the exposure device 17 or records the signal on a memory or the like.

The MFP 10 includes, between the paper feeding part 13 and the photoconductive drum 14, a conveyance mechanism 23 and a register roller pair 24 to convey the sheet P to between the photoconductive drum 14 and the transfer roller 20 in synchronization with the toner image on the photoconductive drum 14.

The MFP 10 discharges the sheet P on which an image is formed by the printer part 11 to the paper discharge tray 30 from a paper discharge part 25. The paper discharge part 25 includes a corrugation roller 26 as a guide part to discharge the sheet from a discharge port 25 a. The corrugation roller 26 includes an upper roller 27 and a lower roller 28.

As shown in FIG. 2, the upper roller 27 of the corrugation roller 26 includes a first roller 27 b at the center of a shaft 27 a, and second rollers 27 c at both sides of the first roller 27 b. The upper roller 27 includes third rollers 27 d at both sides of the shaft 27 a and between the first roller 27 b and the second roller 27 c. The sizes of the outer diameters of the first roller 27 b, the second roller 27 c and the third roller 27 d have a relation of the first roller 27 b>the second roller 27 c>the third roller 27 d. The lower roller 28 of the corrugation roller 26 includes fourth rollers 28 b on a shaft 28 a at positions opposite to the third rollers 27 d. Incidentally, sheet discharge may be performed without using the corrugation roller.

By the structure as stated above, the MFP 10 forms the toner image by the printer part 11 on the sheet P fed from the paper feeding part 13. The MFP 10 discharges the sheet having the toner image to the paper discharge tray 30 by the corrugation roller 26. The image forming apparatus is not limited to this. The image forming apparatus may include plural printer parts such as a printer part using a decolorable toner and a printer part using a non-decolorable toner. The print system of the printer part is not limited to an electrophotographic system, but may be an ink-jet system or the like.

Next, the paper discharge tray 30 will be described in detail. The paper discharge tray 30 includes a tray surface 31 as a placing part on which the sheet P discharged from the corrugation roller 26 is placed, and a rib 32 as a projection. The tray surface 31 is inclined so that the downstream side becomes high in a conveyance direction of an arrow r direction of the sheet P. The rib 32 is provided on the tray surface 31, and includes two apexes of a first apex 32 a and a second apex 32 b. The height of the downstream second apex 32 b is high as compared with the height of the upstream first apex 32 a in the conveyance direction of the arrow r direction of the sheet P.

If the print operation of the MFP 10 is started, the printer part 11 forms the toner image on the sheet P. In the MFP 10, the upper roller 27 and the lower roller 28 of the corrugation roller 26 sandwich the sheet P having the toner image and discharge the sheet to the paper discharge tray 30. As shown in FIG. 2, the section of the sheet P sandwiched between the upper roller 27 and the lower roller 28 is corrugated. The sheet P is corrugated, so that the stiffness is strengthened. The stiffness of the sheet P is strengthened, so that, if the sheet exits from the discharge port 25 a, the front end of the sheet P is prevented from hanging down.

Even if the corrugation roller is not used in the paper discharge part, the section of the sheet P is warped by heat deformation in the fuser 22 and the stiffness may be strengthened.

The sheet P which passes through the corrugation roller 26 and whose stiffness is strengthened advances in the arrow r direction as indicated by a dotted line in FIG. 3. A front end Pf of the sheet P contacts the first apex 32 a of the rib 32. The front end Pf of the sheet P climbs over (passes) the first apex 32 a, and contacts the second apex 32 b of the rib 32.

If the front end Pf of the sheet P contacts the first apex 32 a, the corrugated shape of the front end Pf is broken. For example, if the stiffness of the sheet P is low, the shock of breaking of the corrugated shape of the front end Pf by the first apex 32 a influences a rear part of the sheet P, and the stiffness of the rear part Pr is reduced. The rear part Pr of the sheet P hangs down onto the tray surface 31 as indicated by a solid line in FIG. 3. For example, if the stiffness of the sheet P is high, the shock of breaking of the corrugated shape of the front end Pf by the first apex 32 a does not influence the rear part. Even if the stiffness of the sheet P is high and the stiffness of the rear part Pr is not reduced by the contact with the first apex 32 a, if the front end Pf contacts the second apex 32 b and the corrugated shape of the front end Pf is further broken, the shock influences the rear part of the sheet P and the stiffness of the rear part Pr is reduced.

According to the stiffness corresponding to the paper quality or the environment, for example, the stiffness is reduced by the shock of contact of the front end Pf with the first apex 32 a and the rear part Pr of the sheet P may hang down, or for example, the stiffness is reduced by the shock of contact of the front end Pf with the two apexes of the first apex 32 a and the second apex 32 b and the rear part Pr of the sheet may hang down. Since the rib 32 includes the two apexes of the first apex 32 a and the second apex 32 b, even if the stiffness of the sheet P is high, the stiffness of the sheet P discharged from the corrugation roller 26 is certainly reduced and the sheet P is aligned on the tray surface 31 at the time of paper discharge.

On the other hand, for example, as a comparative example, as shown in FIG. 4, a rib 132 is assumed to include one apex 132 a. For example, if the stiffness of a sheet P is high, even if a front end Pf contacts the apex 132 a, the stiffness of a rear part Pr of the sheet P may not be reduced. If the stiffness of the sheet is not reduced, the sheet P swings around the apex 132 a as a fulcrum as indicated by an arrow “a”. Thus, a succeeding sheet P2 pushes out the preceding sheet P or the succeeding sheet P2 enters under the preceding sheet P, and the alignment property of the sheets P on the tray surface 31 is deteriorated.

According to the embodiment, the rib 32 including the two apexes of the first apex 32 a and the second apex 32 b is arranged on the tray surface 31 of the paper discharge tray 30. If the stiffness of the sheet P is high, the stiffness of the rear part Pr is reduced by the shock of contact of the front end Pf with the second apex 32 b after the shock of contact of the front end with the first apex 32 a. The stiffness of the sheet P is certainly reduced irrespective of the type of the sheet P or the environment, and the alignment property of the sheets P on the tray surface 31 is improved.

The structure and the arrangement of the placing part or the projection of the embodiment are not limited. For example, the number of apexes of the projection maybe two or more. Besides, if the projection includes plural apexes, for example, as in a modified example shown in FIG. 5, a third apex 42 a and a fourth apex 43 a may be formed on different ribs 42 and 43. Alternatively, a projection is made to have a pin shape, and apexes of plural pins may be arranged so that a downstream apex becomes high in a conveyance direction of a sheet P.

While certain embodiments have been described these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel apparatus and methods described herein may be embodied in a variety of other forms: furthermore various omissions, substitutions and changes in the form of the apparatus and methods described herein may be made without departing from the spirit of the inventions. The accompanying claims and there equivalents are intended to cover such forms of modifications as would fall within the scope and spirit of the invention. 

What is claimed is:
 1. A paper discharge tray comprising: a placing part on which a recording medium discharged from a paper discharge part is placed; and a projection which is provided on the placing part and includes a plurality of apexes arranged in a paper discharge direction of the recording medium.
 2. The tray of claim 1, wherein a height of a downstream apex of the plurality of apexes in the paper discharge direction is higher than a height of an upstream apex.
 3. The tray of claim 1, wherein the placing part is inclined and a downstream side of the placing part becomes high in the paper discharge direction of the recording medium.
 4. An image forming apparatus comprising: an image forming part to form an image on a recording medium; a paper discharge part to discharge the recording medium having the image; a placing part on which the recording medium discharged from the paper discharge part is placed; and a projection which is provided on the placing part and includes a plurality of apexes arranged in a paper discharge direction of the recording medium.
 5. The apparatus of claim 4, wherein the paper discharge part includes a guide part to bend the recording medium in a vertical direction to the paper discharge direction.
 6. The apparatus of claim 4, wherein a height of a downstream apex of the plurality of apexes in the paper discharge direction is higher than a height of an upstream apex.
 7. The apparatus of claim 4, wherein the placing part is inclined and a downstream side of the placing part becomes high in the paper discharge direction of the recording medium. 